Devices for performing chemical analysis have in recent years become miniaturized. For example, microfluidic devices have been constructed using microelectronic fabrication and micromachining techniques on planar substrates such as glass or silicon which incorporate a series of interconnected channels or conduits to perform a variety of chemical analysis such as capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC).
Microfluidic substrates have networks of chambers connected by channels which have mesoscale dimensions, where at least one dimension is usually between 0.1 microns and 500 microns. Such microfluidic substrates may be fabricated using photolithographic techniques similar to those used in the semi-conductor industry, and the resulting devices can be used to perform a variety of sophisticated chemical and biological analytical techniques. Microfluidic analytical technology has a number of advantages, including the ability to use very small sample sizes, typically on the order of nanoliters. The substrates may be produced at a relatively low cost, and can be formatted to perform numerous specific analytical operations, including mixing, dispensing, valving, reactions, and detections.
Another recently developed class of sample-receiving microfluidic substrates includes substrates having a capillary interface that allows compounds to be brought onto the test substrate from an external source, and which can be advantageously used in a number of assay formats for high-throughput screening applications. These assay formats include fluorogenic assays, fluorescence polarization assays, non-fluorogenic mobility shift assays, dose response assays, and calcium flux cell-based assays.
Other applications for microfluidic devices include diagnostics involving biomolecules and other analytical techniques such as micro total analysis systems. Such devices, often referred to in the art as “microchips,” also may be fabricated from plastic, with the channels being etched, machined or injection molded into individual substrates. Multiple substrates may be suitably arranged and laminated to construct a microchip of desired function and geometry. In all cases, the channels used to carry out the analyses typically are of capillary scale dimension.
To fully exploit the technological advances offered by the use of microfluidic devices and to maintain the degree of sensitivity for analytical techniques when processing small volumes, e.g., microliters or less, it is critical to have microvalves that are capable of rapid (i)“on” and “off” actuation and/or (ii) diversion of fluid flow from one stream to another.